20160823 - qualities of communications...1 d. w. cearly, b. burke, m. j. walker, top 10 strategic...

QUALITIESOFCOMMUNICATIONSPROTOCOLSANDTHEIRBEARINGON

ENGINEERINGSUCCESSFULSOFTWARESYSTEMS

DR.STEPHENCLYDE

UTAHSTATEUNIVERSITY

SOFTNET,ICSEA2016

ROME,ITALY,AUGUST22-25,2016

2016TECHNOLOGYTRENDS

• 8outofthetop10technologytrends1 directlyinvolveorrequirenetworkcommunications:• DeviceMesh• AmbientUserExperience• InternetofThings• InformationofEverything

• Italmostgoeswithoutsayingthatcommunicationsarebeingintegratedintoallkindsofapplications,e.g.• Smarthomeappliances• Smartmedicaldevices• Personalandbusinessapplicationsofallkinds

1D.W.Cearly,B.Burke,M.J.Walker,Top10StrategicTechnologyTrendsfor2016,Gartner,Feb.29,2016

• AutonomousAgentsandThings• AdaptiveSecurityArchitecture• AdaptiveSystemArchitecture• MeshAppandServiceArchitecture

AFEWRANDOMTHOUGHTSABOUTCOMMUNICATION

• Chickensquawkstobroadcastthatit’slayinganegg

• Itcommunicatesomethingaboutits”state”

• However,thechickendoescareifothershearheroraboutthestateofthelisteners

Verybasiccommunication:TheChickenandEgg


• Uponfindingpollen,ascoutbeereturnstothehiveandperformsafigure-8dance,wheretheorientation,length,andintensityofthewigglescommunicatethelocationofpollen

• Thedancecommunicatesstate,alongwithinstructionsforlocatingpollen• Thescoutbeedoesn’twaitforaresponsefromotherbees,butcompetestobeheard

Aslightlymoresophisticatedexampleofcommunication:TheHoney-beeWiggleDance


• Hewillrepeatthesneezingsoundandheadpointing,ifIdon’trespond• Hecommunicationsinvolveanexchangeofstateorinformation,withsomesynchronizationandreliability

• Itmaybeprimitive,butthere’snodoubtthatwehavea”conversation”

Anevenmoresophisticatedexampleofcommunication:Zazoo’s HeadPointing• Zazoo findsme,makesasortofsneezingsound,pointshisheadinthedirectionhewantsmetogoandwaitsformetofollow.

CONVERSATIONSANDPROTOCOLS

• Aconversation isanseriesofexchanges(messages)amongentities(processes)forthepurposeofaccomplishingsometask

• Themessages,theirsequence,format,semantics,validation,andtherulesthatgoverntheeachprocessesexpectedbehaviorcompriseacommunicationprotocol• i.e.,aprotocolprescribeswhatconversationsareallowed

• Asetofrelatedcommunicationsprotocolsisaprotocolsuite

LAYERSOFCOMMUNICATIONPROTOCOLS

Physical

Link

Network

Transport

Application

System1 System2Application-levelCommunicationProtocols

TCP/UDP

IP

Physical

Link

Network

Transport

Application

APPLICATION-LEVELCOMMUNICATIONPROTOCOLS(ACP’S)

• Definehowthecomponentsofapplicationsoftwaresystemcommunicate• CanbebuiltontopoforcomposedotherofACP’s• Areoftenuniquetoandcustombuiltforanapplication• Althoughtherearemanystandardizationefforts,certainmarketandtechnologicalforcesexistthatworkagainststandardization• Competition• Ongoingneedforincrementalimprovementsinaproduct

• Advancesintechnology• Newuserrequirements

• Changesinuserexpectations• Lackofawarenessofappropriatestandardsbydevelopers

THEPROBLEM

• NewACP’sarebeingwrittenatanacceleratingrate• ThequalityofACP’sseemstovarywidely,e.g.,

• Considercommonfiletransfertools(FTP,SFTP,SCP,filetransferportionofinRDP,etc.)Theycandifferentconsiderablyintransferspeeds.Why?

• ConsidertheSimpleMailTransferProtocol(SMTP).Itscoredocumentationisover30pageslong.Simple?

• Protocolsforexchanginghealthinformation(e.g.,HL7)areoftenhundredsofpages.Whyandhowdoesthissoftwareengineering?

• Theneedforgoodsoftwareengineersisstillgrowing• And,theneedfortrainingtheminimplementingeffectivenetworkcommunicationsparallelsthatgrowth

MOVINGTOWARDSASOLUTION

• Toimprovetheengineeringofapplicationsthathavecommunicationrequirements,weneed• Moreproductivityinthedevelopmentprocess• Waysofestimatedthecharacteristicsofthecommunicationsasystemwillhave• Waysofmeasuringtheactualcharacteristicsofasystemonceitisoperational• Inotherword,higherqualityincommunication

• But,whatis“higherquality”inthecontextofcommunications?• Howcanwediscuss,planfor,implement,andmeasuresuchquality?• Howcanweteachnewdevelopersaboutqualityincommunications?

QUALITYMODELS

• Overthelast40years,therehavebeenmanyqualitymodelsproposedforsoftware(code,softwareproducts)andoperationalprocedures(systemsinuse)• Hereareafew-- someareverygeneral;othersarespecializedforcertainqualitiesortypesof

software

• Over30qualitymodelsexaminedtodate• NonehaveaddressedissuesuniquetoACP’s

1970 1980 1990 2000 2010

QUALITIESà FACTORSà ATTRIBUTESàMETRICS

Qualities

Factors

Attributes

Metrics

Meta-modelforSant’Anna’s Reuseand

MaintainabilityQualityModel(2003)

e.g.,Reuse

e.g.,Flexibility

e.g.,Coupling

e.g.,DepthofInheritanceTree

Meta-modelforISO25010QualityModels

(2008)

Characteristics

Sub-characteristics

Attributes

Metrics

Externallyobservable

Internaltosoftwareoroperations

Twoqualitiesmodels:• SoftwareProduct• SysteminUse

QUALITYMODELSFORACP’S

• Weadaptthemeta-modelofISO25010• Characteristicsà generalcommunicationqualities

• Sub-characteristicsà externallyobservablequalitiesofanACP

• Attributeà concretepropertiesorconditionsoftheACPthatimpactthesub-characteristicsandthatcanbeevaluatedviametrics

• Metricsà waystomeasuretheattributes

• TwoqualitymodelsforACP’s• IdealisticQualityModelforACP’s

• Requirements-orientedQualityModelforACP’s

IDEALISTICQUALITYMODELFORACP’S

• IncludescharacteristicsthatallACP’sshouldtrytoachievetosomedegree,limitedonlybydevelopmentresources(developers)andtime

• Notethatthecharacteristicsmayoverlaporconflict• Achievingonemaymakeiteasierorhardertoachieveanother

• Characteristics:• FunctionalSuitability• Operability• Security• Performanceefficiency

• Maintainability

• Extensibility

• Simplicity

FUNCTIONALSUITABILITY

ThedegreetowhichtheACPmeetsstatedandimpliedneedsSub-characteristic Description Attributes

AppropriatelyAccommodating

Thedegreetowhichthe ACPallowsexpectedconversations

• Involves appropriate participants(e.g.,processes)• Authenticatesparticipants• Includes exchangesofnecessarystateinformationatthe

righttime• Usesappropriatemessagesthattriggerdesired

behaviorsinreceivingprocessesAppropriatelyRestrictive

ThedegreetowhichtheACPprohibits invalidorundesirableconversations

• Excludesinappropriateorunauthorized participants• Definesbehaviorsforillegalmessagesormessage

sequences

Compliance Thedegreetowhichitusesexistingstandards

• Buildsonorintegratesexistingstandards(messageformat,encoding/decoding,establishingconnections,authentication,etc.)werepossible

OPERABILITY

ThedegreetowhichtheACPcanbeunderstood,learned,operate

Sub-characteristic Description Attributes

Recognizable ThedegreetowhichadevelopercanrecognizewhethertheACPisappropriatefortheirneeds

• Has aclear,complete,andupdate documentation• Uses standardorcommonterms• Usesdesignpatterns

Learnable ThedegreetowhichdeveloperscanlearnhowtoimplementtheACPinanapplication

• Has aclear,complete,andupdate documentation• Usesstandardmessageformats,encoding,etc.• Uses standardorcommonterms

Easy toOperate Theease ofwhichnetworkadministratorscanensurethattheconversationsfollowingthisACPcansucceed

• Numberandtypeofnetworksinvolved• Whetherparticipantshasdynamicaddresses• Requiresports• RequirestunnelingorVPNconnections• Requirescertificatesandhowtheyaredistributed

SECURITYThedegreetowhichtheACPprotectsagainstaccidentalordeliberatemisuse,unauthorizedaccess,ordestructionofthecommunicatingprocesses,resourcestheymanage,ornetworkSub-characteristic Description Attributes

Authenticity Thedegreetowhichthe ACPguaranteesthatparticipantsare who/whattheyclaimedtobe

• Typeofauthentication(e.g.,certificates)• Verification(e.g.,certificateauthority)

Confidentiality Thedegreetowhichthe ACPguaranteesthatprivatedataarenotaccessibletounauthorizedparties

• Typeofencryptionofdata

Integrity Thedegree towhichtheACPguaranteesthatmessagesarenotcorruptedortamperedwith

• Typeofencryption• Type oferror detectionandcorrection

Non-repudiation Thedegreetowhichactionsoreventscanbeproventohavetakenplace,sothattheeventsoractionscannotberepudiatedlater

• Usesdigitalsignatures• Typeofsynchronization

Accountability Thedegreetowhichconversationscanbetraced tocommunicatingprocesses

• Typeofaddressingoridentification• Typeofauthentication• Messageprovenance

PERFORMANCEEFFICIENCYThedegreetowhichACPprescribesconversationthathaveappropriateperformance,intermsofresponsetimes,turnaroundtimes,andtotalthroughputSub-characteristic Description Attributes

Response times Thedegree towhichtheACPsupportsconversationswherecommunicatingprocessquicklybecomeawareofotherstateandthattheconversationisproceeding

• Message-to-Message time

Turnaroundtimes ThedegreetowhichtheACPallowsindividualconversationstocompleteinanappropriateamountoftime

• Conversationstart-end time

Totalthroughput ThedegreetowhichtheACP supportsanappropriatenumberofconversationswithinafixedaboutoftime

• Completed Conversations peruntiloftime

MAINTAINABILITYThedegreetowhichACPcanbemodified


Modularity Thedegree towhichaACPisbrokenupintoloosingcouplingphasesorsub-protocol

• Message sequencecomplexity• Presenceandnumberofsub-protocols

Cohesion Thedegree towhichindividualmessagesorsub-protocolsarefocusedonasinglepurpose

• Unity ofpurposeforindividualmessages• Unityofpurposeforsub-protocols

Reuse The degreetowhichanACPcanbere-usedforpurposesotherthantheoriginalone

• Numberofuses inotherapplications

Testability ThedegreetowhichanACPcanbetested • Supportformockable process• Supportformockable messages• Deterministic

EXTENSIBILITY


Open messagestructure

The degreetowhichthemessages(theircontentandstructure)canbeextended

• Type ofmessages• Messageencoding• Useofstandards

Openmessagesequence

Theamountofflexibilityintheacceptablemessagesequences

• Stateless operations• Unconstrainedmessagesequences

ThedegreetowhichACPcanbeextended

SIMPLICITY


Minimalmessagesequences

Whether anymessageintheACPcanbeeliminatedorcombinedwithanotherwithoutcompromisingthefunctionality,reliability,synchronization

• Structure ofthemessage sequences

Minimal messagecontent

Whetheranycontent ofanymessageintheACPbeeliminatedorcombinedwithanothermessagewithoutcompromising,reliability,orsynchronization

• Messagepayloads

ThedegreetowhichtheACPcontainsnoaccidentalcomplexity

REQUIREMENTS-ORIENTEDQUALITYMODELFORACP’S

• ThedegreetowhichthecharacteristicsinthismodelSHOULDbeobtaineddependsontheapplicationrequirements,notonresourcesortime.• Withthismodel,a“good”ACPiswhen“TheACPsupportstheappropriatedegreeof_______forthis application”,wheretheblankisthecharacteristics

• Characteristics:• Reliability

• Synchronicity

• Longevity

• Adaptabilityforscalabledistribution

• Resourceutilization

RELIABILITYThedegreetowhichacommunicatingprocesscanobtainanassurancethattheintendedreceiversofsomemessagecorrectlyreceivedandreactedtothatmessageSub-characteristic Description Attributes

Detectable Thedegree towhichaparticipantinaconversationcandetectsuccessfullycompletedorfailedconversations

• Typeofmessageidentity• Requiresmessagestobesentafteroperations,

particularlystate-changingoperations• Requiresacknowledgementsshortlyaftermessage

receipts• Supportheart-beatorprobemessages

Fault Tolerant ThedegreetowhichACP canallowconversationtorecoverfromnetwork,server,orprocessfailures

• Allowsfordetectionoflostmessagesandcontinuationoftheconversation

• Allowsfordetectionofcorruptedoralteredmessagesandthecontinuationoftheconversation

• Allowsfordetectionandresolutionofduplicatemessages

• Allowsfordetectionandresolutionofout-of-ordermessages

SYNCHRONICITY

Theamountofinter-processcoordinationneededinadistributedsystemrelativetoexecutionofactionsinadistributedsystemSub-characteristic Description Attributes

InformedOperations Thedegreetowhichacommunicating processthatneedperformanaction receivesnecessaryorusefulinformationfromotherprocesses

• Numberofconversation-relatedoperationsthatrequireinformationfromotherprocesses

• Numberofthoseoperationsareproceededbymessageswiththenecessaryorusefulinformation

Minimize Waiting Thedegree towhichacommunicatingprocesscanproceedwithoperationsrelatedtotheconversationwithoutwaitingforinformationfromotherprocesses

• Numberofblocked-waiting-for-replystates• Expectedturnaroundtimesthemessagesequences

thatcauseaprocesstoenterandleaveablocked-waiting-for-replystates

LONGEVITY

ThedegreetowhichanACPcansupportlong-runningconversationscausedbylong-runningoperations


Notification Thedegreetowhichaprocesscanletother processknowthatitisbeginning,workingon,orendingalong-runningprocess

• Whethertheconversationtriggerslong-runningoperationsandothersneedtobeawareoftheirprogressorcompletion

Awareness Thedegreetoa processcantracktheprogressofalong-runningoperationinanotherprocess

• Whethertheprotocolallowslong-runningoperationstobedividedintotosequentialstepsorparalleltasks

• Usesstatemessagestoinformothersofprogress

ADAPTABILITYFORSCALABLEDISTRIBUTION

ThedegreetowhichanACPcansupportscalabilitydistribution(increaseinresourceand/ornumberofprocesses)


Resource Scalability Thedegree towhichtheACPallowsforanincreaseinthenumberofresources

• Typeofresourcenameresolution• Supportslocationtransparency• Supportsmigrationtransparency• Supportsreplicationtransparency

Process Scalability Thedegree towhichtheACPallowsforanincreaseinthenumberofprocesses(resourceusers)

• Typeofprocessnameresolution• Supportslocationtransparency• Supportsmigrationtransparency• Supportsreplicationtransparency

ConcurrentConversationScalability

Thedegree towhichtheACPallowsforanincreaseinthenumberofconcurrentconversations

• Supportslocationtransparency• Supportsmigrationtransparency• Supportsreplicationtransparency

RESOURCEUTILIZATION

ThedegreetowhichanACPcanutilizesavailablecomputation,data,andnetworkresourcestomaximizeoverallsystemthroughputand/orreduceresponsetimes.


LoadBalancing ThedegreetowhichtheACPcan supportthebalancingofworkloadsacrossdevicesandadheretoprescribedconstraintsontheutilizationofindividualcomputableresources

• Exchangesdeviceloadinformation• Allowsforestimationofdevice

loads• Supportslocationtransparency• Supportsmigrationtransparency• Supportsreplicationtransparency

Bandwidth Balancing Thedegree towhichtheACPcansupportthereshapingofnetworktraffictoavoidcongestionandadheretoprescribedconstraintsontheindividualorlinkutilization

• Supports”qualityofservice”controls

• Supportslocationtransparency• Supportsmigrationtransparency• Supportsreplicationtransparency

WORKINPROGRESS

• Continuetorefinethecharacteristics,sub-characteristics,andattributesofeachmodel

• Adopt,adapt,ordevelopmetricsfortheattributes• UsethemodelstoevaluateexistingACP’s

• Studytherelationshipsbetweencharacteristics• Iteratetheabove

IMPACTONSOFTWAREENGINEERING

• WithoutanynotionofqualityforACP’s,developerswillbeguessingorcostlytrail-n-errorapproachtocreatinganyapplicationthatrequiresnetworkcommunication

• WithaqualitymodelforACP’s,developerswould• Haveabasisforformalizingstaticmetrics,whichuseACPdesignsasinput• UsethosemetricscouldpredicateanACP’sattributes,andinturnitssub-characteristicsandcharacteristics

• Beabletoanswerquestions,like• Aretherequirement-orientedcommunicationcharacteristicsagoodfit• Aretheidealisticcommunicationcharacteristicsachievablewiththeavailableresourcesandtime

IMPACTONSOFTWAREENGINEERING

(continued)• Beabletobuilddesigntoolsthat helpdevelopersdecidethedegreetowhichcharacteristicsshouldandaidinthedesignofACP’s

• Capturecommunication-designexpertiseindesignpatterns

• Furthermore,educatorscouldimprovecurriculatobetterpreparestudentforbuildingstate-of-the-artsoftwareapplications

• And,technologyprofessionalwouldhaveabasisforevaluating,comparing,andrecommendingsoftwareapplications

FUTUREWORK

• Formallydocument• IdealisticQualityModelforACP’s

• Requirements-orientedQualityModelACP’s

• Developtoolsfor• Guidingdevelopersinchoosingappropriatetargetdegreeofsupportforeachcharacteristic

• CapturingACPdesignsinastructuredform

• Computingmeasurementbasedonthemetrics

• Estimatingtheattributes,sub-characteristics,characteristicsofaprotocolorentireprotocolsuite

• Designandconductempiricalstudiestovalidthemodelsandmetrics

20160823 - qualities of communications...1 d. w. cearly, b. burke, m. j. walker, top 10 strategic...

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